Smoothing surface roughness of iii-v semiconductor fins formed from silicon mandrels by regrowth

ABSTRACT

A method of forming a III-V semiconductor vertical fin is provided. The method includes forming a fin mandrel on a substrate, forming a spacer layer on the substrate surrounding the fin mandrel, forming a wetting layer on each of the sidewalls of the fin mandrel, forming a fin layer on each of the wetting layers, removing the fin mandrel, removing the wetting layer on each of the fin layers, and forming a fin layer regrowth on each of the sidewalls of the fin layers exposed by removing the wetting layer from each of the fin layers.

BACKGROUND Technical Field

The present invention generally relates to alleviating surface roughnesson grown III-V semiconductor fins, and more particularly to epitaxiallygrowing III-V semiconductor on the rough mandrel growth face of III-Vsemiconductor fins.

Description of the Related Art

A Field Effect Transistor (FET) typically has a source, a channel, and adrain, where current flows from the source to the drain, and a gate thatcontrols the flow of current through the channel. Field EffectTransistors (FETs) can have a variety of different structures, forexample, FETs have been fabricated with the source, channel, and drainformed in the substrate material itself, where the current flowshorizontally (i.e., in the plane of the substrate), and FinFETs havebeen formed with the channel extending outward from the substrate, butwhere the current also flows horizontally from a source to a drain. Thechannel for the FinFET can be an upright slab of thin rectangularsilicon (Si), commonly referred to as the fin with a gate on the fin, ascompared to a MOSFET with a single gate parallel with the plane of thesubstrate. Depending on the doping of the source and drain, an n-FET ora p-FET can be formed.

Examples of FETs can include a metal-oxide-semiconductor field effecttransistor (MOSFET) and an insulated-gate field-effect transistor(IGFET). Two FETs also can be coupled to form a complementary metaloxide semiconductor (CMOS) device, where a p-channel MOSFET andn-channel MOSFET are coupled together.

With ever decreasing device dimensions, forming the individualcomponents and electrical contacts becomes more difficult. An approachis therefore needed that retains the positive aspects of traditional FETstructures, while overcoming the scaling issues created by formingsmaller device components.

SUMMARY

In accordance with an embodiment of the present invention, a method offorming a III-V semiconductor vertical fin is provided. The methodincludes forming a fin mandrel on a substrate. The method furtherincludes forming a spacer layer on the substrate surrounding the finmandrel. The method further includes forming a wetting layer on each ofthe sidewalls of the fin mandrel. The method further includes forming afin layer on each of the wetting layers. The method further includesremoving the fin mandrel, removing the wetting layer on each of the finlayers, and forming a fin layer regrowth on each of the sidewalls of thefin layers exposed by removing the wetting layer from each of the finlayers.

In accordance with another embodiment of the present invention, a methodof forming a III-V semiconductor vertical fin is provided. The methodincludes forming a fin mandrel on a substrate. The method furtherincludes forming a spacer layer on the substrate surrounding the finmandrel. The method further includes forming a wetting layer on each ofthe sidewalls of the fin mandrel. The method further includes forming afin layer on each of the wetting layers, where the fin layer is a binaryor ternary III-V semiconductor material. The method further includesremoving the fin mandrel and removing the wetting layer on each of thefin layers. The method further includes forming a fin layer regrowth oneach of the sidewalls of the fin layers exposed by removing the wettinglayer from each of the fin layers, and forming a dummy gate layer over amiddle section of a vertical fin including the fin layer regrowth andthe fin layer.

In accordance with yet another embodiment of the present invention, aIII-V semiconductor vertical fin device is provided. The III-Vsemiconductor vertical fin device includes a spacer layer on asubstrate, wherein the material of the spacer layer is a flowable oxide,a vertical fin on the spacer layer, where the vertical fin is a binaryor ternary III-V semiconductor material, and a gate structure over amiddle section of the vertical fin.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description will provide details of preferred embodimentswith reference to the following figures wherein:

FIG. 1 is a cross-sectional side view showing a plurality of finmandrels formed on a substrate and a mandrel template on each finmandrel, in accordance with an embodiment of the present invention;

FIG. 2 is a cross-sectional side view showing a spacer layer betweeneach pair of the plurality of fin mandrels, in accordance with anembodiment of the present invention;

FIG. 3 is a cross-sectional side view showing a wetting layer on thesidewalls of each fin mandrel and mandrel template, in accordance withan embodiment of the present invention;

FIG. 4 is a cross-sectional side view showing a fin layer formed on thewetting layers on each of the fin mandrels and mandrel templates, inaccordance with an embodiment of the present invention;

FIG. 5 is a cross-sectional side view showing a fill layer on the finlayers and mandrel templates, in accordance with an embodiment of thepresent invention;

FIG. 6 is a cross-sectional side view showing removal of extraneous finlayer islands from the top surface of the mandrel templates, inaccordance with an embodiment of the present invention;

FIG. 7 is a cross-sectional side view showing the fin layers, wettinglayers, fin templates, and spacer layer after removing the fill layer,in accordance with an embodiment of the present invention;

FIG. 8 is a cross-sectional side view showing the fin layers and wettinglayers on the spacer layer after removing the fin templates and reducingthe height of the fin mandrels, in accordance with an embodiment of thepresent invention;

FIG. 9 is a cross-sectional side view showing the fin layers afterremoving the wetting layers, in accordance with an embodiment of thepresent invention;

FIG. 10 is a top view showing the dummy gate layer formed on a middlesection of the fin layers, and fin layer regrowth on the rough sidewallsof the fin layers, in accordance with an embodiment of the presentinvention;

FIG. 11 is a cross-sectional side view showing the dummy gate layerformed on a portion of the fin layers along the A-A cutting plane ofFIG. 10, in accordance with an embodiment of the present invention;

FIG. 12 is a top view showing source/drains formed on the fin layers andfin layer regrowth on opposite sides of the dummy gate layer, inaccordance with an embodiment of the present invention;

FIG. 13 is a cross-sectional side view showing source/drains on the finlayers and fin layer regrowths along the B-B cutting plane of FIG. 12,in accordance with an embodiment of the present invention;

FIG. 14 is a top view showing cover layers formed on the source/drainson opposite sides of the dummy gate layer, in accordance with anembodiment of the present invention;

FIG. 15 is a cross-sectional side view showing the cover layer on thesource/drains along the B-B cutting plane of FIG. 14, in accordance withan embodiment of the present invention;

FIG. 16 is a top view showing the fin layers and an oxide layer exposedafter removing the dummy gate layer from between the cover layers, inaccordance with an embodiment of the present invention;

FIG. 17 is a top view showing the fin layer regrowth on the middlesection of the fin layers to form a plurality of vertical fins on thespacer layer, in accordance with an embodiment of the present invention;

FIG. 18 is a cross-sectional side view showing the fin layer regrowth onthe middle section of the fin layers along the A-A cutting plane of FIG.17, in accordance with an embodiment of the present invention; and

FIG. 19 is a top view showing a gate structure formed on the middlesection of the vertical fins, in accordance with an embodiment of thepresent invention.

DETAILED DESCRIPTION

Embodiments of the present invention relate generally to growing III-Vsemiconductor fins on a wetting layer, removing the wetting layer, andgrowing additional III-V semiconductor material to smooth the roughsurface exposed by removing the wetting layer.

Embodiments of the present invention also relate generally to smoothingthe rough face of a III-V semiconductor fin by additional epitaxialgrowth of the III-V semiconductor fin. III-V semiconductor fins grown on(111) silicon mandrel sidewalls can have excessively rough surfaces atthe Si/III-V semiconductor interface that can reduce and/or limitelectron transport properties of subsequently fabricated devices. TheSi/III-V interface can be significantly rougher than the exposed growthfront of the fin.

Embodiments of the present invention also relate generally to smoothingthe rough face of a III-V semiconductor fin by growing the additionalIII-V material before replacement of a dummy gate structure. Thick III-Vsemiconductor fins can be thinned to a final width by using a digitaletch (e.g., a plasma oxidation and acid rinse).

Exemplary applications/uses to which the present invention can beapplied include, but are not limited to: Complementarymetal-oxide-semiconductor devices and static random access memorydevices, where the present invention can be applied to transistorshaving high speed or lower power usage in the logic and memory devices.

It is to be understood that aspects of the present invention will bedescribed in terms of a given illustrative architecture; however, otherarchitectures, structures, substrate materials and process features andsteps can be varied within the scope of aspects of the presentinvention.

Referring now to the drawings in which like numerals represent the sameor similar elements and initially to FIG. 1, a cross-sectional side viewof a plurality of fin mandrels formed on a substrate and a mandreltemplate on each fin mandrel is shown, in accordance with an embodimentof the present invention.

In one or more embodiments, a substrate 110 can be, for example, asingle crystal semiconductor material wafer or asemiconductor-on-insulator stacked wafer. The substrate can include asupport layer that provides structural support, and an activesemiconductor layer that can form devices. An insulating layer may bebetween the active semiconductor layer and the support layer to form asemiconductor-on-insulator substrate (SeOI) (e.g., asilicon-on-insulator substrate (SOI)). In one or more embodiments, thesubstrate can be a single crystal silicon wafer.

The active semiconductor layer can be a crystalline semiconductor, forexample, a IV or IV-IV semiconductor (e.g., silicon (Si), siliconcarbide (SiC), silicon-germanium (SiGe), germanium (Ge)), or a III-Vsemiconductor (e.g., gallium-arsenide (GaAs), indium-phosphide (InP),indium-antimonide (InSb)). In various embodiments, substrates withcrystal structures similar to silicon single crystal that can form (111)crystal planes can be used.

In one or more embodiments, one or more fin mandrels 120 can be formedon the substrate 110. The fin mandrels 120 can be formed from thesubstrate by masking portions of the substrate with mandrel templates130 having the predetermined dimensions of the fin mandrel, and etchingthe substrate using a crystallographic wet etch, such as tetramethylammonium hydroxide (TMAH)), that can etch essentially straight sidewalls122 for the fin mandrels 120, or a combination of a directional etch(e.g., Reactive Ion Etch (RIE)) and crystallographic wet etch. Thecrystallographic wet etch can be used to obtain a smooth face forepitaxial growth, where the (111) crystal face can be atomically smooth.

In various embodiments, the mandrel templates 130 can be a hardmask, forexample, silicon oxide (SiO), silicon nitride (SiN), silicon oxynitride(SiON), silicon boronitride (SiBN), silicon carbonitride (SiCN), siliconborocarbonitride (SiBCN), or a combination thereof.

In various embodiments, the fin mandrels 120 can be single crystalsilicon, where the fin mandrels 120 are formed from a single crystalsilicon substrate 110. The mandrel templates 130 and fin mandrels 120can be aligned with the crystal planes of the single crystal substrate,such that the exposed faces of the sidewalls 122 of the fin mandrels 120are {111} silicon crystal faces.

FIG. 2 is a cross-sectional side view showing a spacer layer betweeneach pair of the plurality of fin mandrels, in accordance with anembodiment of the present invention.

In one or more embodiments, a spacer layer 140 can be formed on theexposed surface of the substrate 110, where the spacer layer 140 can bebetween adjacent pairs of the fin mandrels 120. The spacer layer cansurround each of the fin mandrels on the substrate 110.

In various embodiments, the spacer layer 140 can be made of a dielectricmaterial, including, but not limited to a flowable oxide (e.g., hydrogensilsesquioxane (HSQ)) or a silicon oxide (SiO). The flowable oxide canbe blanket deposited on the substrate 110, mandrel templates 130, andfin mandrels 120, and flowable oxide extending above the mandreltemplates 130 removed using a chemical-mechanical polishing (CMP). Thesilicon oxide can be formed using a high density plasma (HDP) and excesssilicon oxide removed using CMP. The spacer layer 140 can be recessed toa predetermined height by a controlled, selective etch to expose apredetermined height of the fin mandrel sidewalls 122.

In various embodiments, the fin mandrels 120 can have exposed sidewalls122 with a height in the range of about 30 nm to about 70 nm, or in therange of about 30 nm to about 50 nm, or in the range of about 50 nm toabout 70 nm, after recessing the spacer layer 140. The exposed finmandrel sidewalls can have a (111) crystal face.

FIG. 3 is a cross-sectional side view showing a wetting layer on thesidewalls of each fin mandrel and mandrel template, in accordance withan embodiment of the present invention.

In one or more embodiments, a wetting layer 150 can be formed on theexposed sidewalls 122 of the one or more fin mandrels 120, where theexposed sidewalls 122 can be {111} crystal faces. The wetting layer 150can be formed by a metal-organic chemical vapor deposition (MOCVD) oratomic layer deposition/atomic layer epitaxy (ALD/ALE). In variousembodiments, the wetting layer 150 forms on the exposed sidewalls 122 ofthe one or more fin mandrels 120 without forming on the exposed topsurface of the spacer layer 140. The wetting layer 150 may form on thetop surfaces of the mandrel templates 130, but not on the surface of thespacer layer 140.

In various embodiments, the wetting layer 150 can be made of III-Vsemiconductor materials, for example, aluminum arsenide (AlAs) or indiumphosphide (InP). The wetting material can be selected based on theability to deposit on {111} crystal faces of the exposed sidewalls 122of the fin mandrels. The crystal lattice of the wetting material may notbe matched to the {111} crystal faces of the sidewalls 122.

In various embodiments, the wetting layer 150 can have a thickness onthe sidewalls of the fin mandrels 120 in the range of about 1 nm toabout 10 nm, or in the range of about 1 nm to about 2 nm, or in therange of about 5 nm to about 7 nm, where the wetting layer issufficiently thick to completely cover each the sidewalls 122 of the finmandrels 120.

FIG. 4 is a cross-sectional side view showing a fin layer formed on thewetting layers on each of the fin mandrels and mandrel templates, inaccordance with an embodiment of the present invention.

In one or more embodiments, a fin layer 160 can be formed on each of thewetting layers 150, where the fin layer 160 can be a binary or ternaryIII-V semiconductor material. The fin layer can be formed by aheteroepitaxial growth process, where the fin layer 160 can growlaterally on the wetting layer 150 from the sidewalls of the fin mandrel120. The fin layer 160 can be formed by a metal-organic chemical vapordeposition (MOCVD) or atomic layer deposition/atomic layer epitaxy(ALD/ALE). In various embodiments, the fin layer 160 forms on thewetting layers 150 without forming on the exposed top surface of thespacer layer 140. Fin layer islands 165 can form on the tops surfaces ofthe mandrel templates 130, for example, when the mandrel templates 130are silicon nitride (SiN), from extraneous material forming the finlayer 160. The fin layer islands 165 can be randomly oriented singlecrystals or polycrystalline deposits of the III-V fin layer material.

In various embodiments, the fin layer 160 can be made of a binary ortertiary III-V semiconductor material, including, but not limited to,indium phosphide (InP), indium arsenide (InAs), indium-gallium-arsenide(InGaAs), and combinations thereof (e.g., multilayers,heterostructures).

In various embodiments, the fin layer 160 can be grown to a thickness inthe range of about 10 nm to about 35 nm, or in the range of about 10 nmto about 30 nm, or in the range of about 15 nm to about 25 nm, where thesmoothness of the exposed surface of the fin layer can improve withincreasing thickness.

FIG. 5 is a cross-sectional side view showing a fill layer on the finlayers and mandrel templates, in accordance with an embodiment of thepresent invention.

In one or more embodiments, a fill layer 170 can be formed on the finlayers 160, wetting layers 150, fin layer islands 165, exposed portionsof the mandrel templates 130, and exposed portions of the spacer layer140.

In various embodiments, the fill layer 170 can be made of amorphoussilicon (a-Si), amorphous carbon (a-C), a flowable oxide (e.g. polymericsilicon oxides (SiO), for example, HSQ), a spin-on-glass, or an organicresist material/organic planarization material. In various embodiments,a fill layer 170 made of a flowable oxide may be densified. The filllayer 170 can be formed to a height that covers the tops of theextraneous fin layer islands 165. The top surface of the fill layer 170can be chemically-mechanically polished to provide a smooth, flatsurface.

FIG. 6 is a cross-sectional side view showing removal of extraneous finlayer islands from the top surface of the mandrel templates, inaccordance with an embodiment of the present invention.

In one or more embodiments, an upper portion of the fill layer 170 andthe fin layer islands 165 can be removed, where the upper portion of thefill layer 170 and the fin layer islands 165 can be removed by achemical-mechanical polishing (CMP). The top surface of the mandreltemplates 130 can be exposed after the CMP.

FIG. 7 is a cross-sectional side view showing the fin layers, wettinglayers, fin templates, and spacer layer after removing the fill layer,in accordance with an embodiment of the present invention.

In one or more embodiments, the fill layer 170 can be removed after theCMP to re-expose portions of the fin layers 160, wetting layers 150, fintemplates 130, and spacer layer 140, where the fill layer 170 can beremoved using a selective etch.

FIG. 8 is a cross-sectional side view showing the fin layers and wettinglayers on the spacer layer after removing the fin templates and reducingthe height of the fin mandrels, in accordance with an embodiment of thepresent invention.

In one or more embodiments, the fin templates 130 can be removed fromthe top surfaces of the fin mandrels 120, where the fin templates 130can be removed using a selective wet or dry etch, for example, RIE, dryplasma etch, basic oxide etch (BOE), phosphoric acid, etc.

In one or more embodiments, the height of the fin mandrels 120 can bereduced to form fin mandrel slabs 125, where the height of the finmandrels can be reduced to expose the sidewalls of the wetting layers150. The height of the fin mandrels 120 can be reduced below the topsurfaces of the spacer layer 140, such that the entire sidewall of thewetting layers 150 are exposed. The top surfaces of the fin mandrelslabs can be less than the height of the spacer layer 140. The height ofthe fin mandrels 120 can be reduced using a selective wet or dry etch.The spacer layer 140 can support the fin layers 160 and wetting layers150 after removal of the fin mandrels from the wetting layers.

FIG. 9 is a cross-sectional side view showing the fin layers afterremoving the wetting layers, in accordance with an embodiment of thepresent invention.

In one or more embodiments, the wetting layers 150 can be removed toexpose the rough sidewalls 167 of the fin layers 160. The wetting layers150 can be removed using a wet chemical etch, for example, hydrochloricacid (HCl) etch or ammonium hydroxide (NH₄OH) etch. In variousembodiments, the wetting layers 150 and fin mandrels 120 can be etchedat the same time. A dry plasma etch or hydrogen fluoride (HF) etch maynot be used.

FIG. 10 is a top view showing the dummy gate layer formed on a middlesection of the fin layers, and fin layer regrowth on the rough sidewallsof the fin layers, in accordance with an embodiment of the presentinvention.

In one or more embodiments, a dummy gate layer 180 can be formed acrossa central portion of one or more of the fin layers 160. The fin layers160 can be masked, and a trench formed in the mask over a predeterminedportion of the fin layers, where the dummy gate layer 180 can be formedacross a central portion of one or more of the fin layers 160.

In various embodiments, the dummy gate layer 180 can define a gatelength of a subsequently formed gate structure on the vertical fins. Thedummy gate layer 180 can have a width in the range of about 10 nm toabout 1 μm, or in the range of about 20 nm to about 100 nm, or in therange of about 10 nm to about 70 nm, or in the range of about 10 nm toabout 30 nm.

In various embodiments, the dummy gate layer 180 can be made of amaterial, including, but not limited to, amorphous silicon (a-Si),amorphous carbon (a-C), silicon-germanium (SiGe), flowable oxide, orsilicon nitride (SiN). The material of the dummy gate 180 canselectively etchable relative to the spacer layer 140 and subsequentlyformed cover layers, or the material of the dummy gate and spacer layercan be the same.

In one or more embodiments, fin layer regrowth 220 can be formed on theexposed rough sidewalls 167 of the fin layers 160, where the fin layerregrowth 220 can be formed by epitaxial growth. The fin layer 160 andfin layer regrowth 220 can form the two components of a vertical fin190. The fin layer regrowth 220 can be formed on the exposed roughsidewalls 167 of the fin layers 160 before or after the dummy gate layeris formed. The fin layer regrowth 220 can be the same III-Vsemiconductor material as the fin layer 160 III-V semiconductormaterial.

FIG. 11 is a cross-sectional side view showing the dummy gate layerformed on a portion of the fin layers along the A-A cutting plane ofFIG. 10, in accordance with an embodiment of the present invention.

In one or more embodiments, the dummy gate layer 180 can extend abovethe top surfaces of the fin layers 160, and fill in the shallow areaover the fin mandrel slabs 125. The mask material can be removed afterformation of the dummy gate layer 180.

FIG. 12 is a top view showing source/drains formed on the fin layers andfin layer regrowth on opposite sides of the dummy gate layer, inaccordance with an embodiment of the present invention.

In one or more embodiments, source/drains 200 can be formed on oppositesides of the dummy gate layer 180 on the exposed portions of the finlayers 160 and fin layer regrowth 220 forming the vertical fins 190. Thesource/drains 200 can be formed by epitaxial growth on the exposedsurfaces of the vertical fins 190 adjacent to the dummy gate layer 180.The epitaxial growth can be terminated before the source/drains 200merge across all the fin layers 160, or the source/drains 200 can growlaterally until source/drains 200 on adjacent fin layers merge. Sectionsof the fin mandrel slabs 125 can be exposed between adjacent, unmerged,source/drains 200. Merged source/drains can cover the fin mandrel slabs125 and prevent shorting and substrate leakage from metal contacts.

In various embodiments, the source/drains 200 can be made of the samematerial as the fin layers 160 and fin layer regrowths 220, where thesource/drains are formed by epitaxial growth on single crystal finlayers 160 and fin layer regrowths 220. In various embodiments, a layerof InAs can be formed on the source/drains 200 to improve electricalcontact.

In various embodiments, the source/drains can be doped with an n-typedopant to form an N-type fin field effect transistor (FinFET).

FIG. 13 is a cross-sectional side view showing source/drains on the finlayers and fin layer regrowths along the B-B cutting plane of FIG. 12,in accordance with an embodiment of the present invention.

In one or more embodiments, a source/drain 200 can be formed on threesides of one or more adjacent fin layers 160 and fin layer regrowths220, where the source/drain 200 can grow from the exposed surfaces ofthe fin layer 160. The source/drain 200 can overhang an edge of thespacer layer, where a portion of the bottom surface of the source/draincan be exposed. Adjacent source/drains 200 can grow to a size at whichthey merge into a single source/drain 200 spanning two or more adjacentfin layers 160 and fin layer regrowths 220 forming the vertical fins.There can be a gap between the merged source/drain 200 and top surfaceof the fin mandrel slab 125.

In various embodiments, an oxide layer 129 can form on the fin mandrelslabs 125, where the oxide layer 129 can be a native oxide layer (e.g.,silicon oxide (SiO)) formed from the fin mandrel slab material. Theoxide layer 129 can be thinner than the depth of the gap between thebottom surface of the source/drains 200 or merged source/drain 200 andthe top surface of the fin mandrel slab 125, so there can still be a gapbetween the merged source/drain 200 and surface of the oxide layer 129,or the oxide layer can be sufficiently thick to fill the gap. A nativeoxide layer can remain, since a hydrogen fluoride (HF) etch may not beused. The oxide layer 129 can prevent formation of the III-V fin layerregrowth 220 on the fin mandrel slabs 125.

FIG. 14 is a top view showing cover layers formed on the source/drainson opposite sides of the dummy gate layer, in accordance with anembodiment of the present invention.

In one or more embodiments, a cover layer 210 can be formed over thesource/drains 200 and the fin mandrel slabs 125, where the cover layercan fill in the gaps between the source/drains 200. The cover layer canbe a dielectric material that physically and electrically isolatesadjacent source/drains 200. The cover layer can be formed by CVD, aspin-on process, or HDP. The dummy gate material can be selectivelyetchable relative to the cover layer 210.

In various embodiments, the cover layer 210 can be flowable oxide,silicon oxide (SiO), silicon nitride (SiN), or a combination thereof. ACMP can be used to remove excess cover layer 210 and planarize the coverlayer 210 at the level of the top of the dummy gate layer 180.

FIG. 15 is a cross-sectional side view showing the cover layer on thesource/drains along the B-B cutting plane of FIG. 14, in accordance withan embodiment of the present invention.

In various embodiments, the cover layer 210 can extend above the topsurfaces of the source/drains 200 and fill in the gaps between thesource/drains.

FIG. 16 is a top view showing the fin layers and an oxide layer exposedafter removing the dummy gate layer from between the cover layers, inaccordance with an embodiment of the present invention.

In one or more embodiments, the dummy gate layer 180 can be removed,where the dummy gate layer can be removed using a selective isotropicetch (e.g., a wet chemical etch). Removal of the dummy gate layer canexpose the central portion of the fin layers 160, spacer layer 140, andoxide layer 129 on fin mandrel slabs 125, between the source/drains 200and the cover layers 210.

FIG. 17 is a top view showing the fin layer regrowth on the middlesection of the fin layers to form a plurality of vertical fins on thespacer layer, in accordance with an embodiment of the present invention.

In one or more embodiments, fin layer regrowth 220 can be formed on theexposed rough surfaces of the fin layers 160, where the fin layerregrowth 220 can be formed by epitaxial growth. The fin layer regrowth220 can be the same III-V semiconductor material as the fin layer 160III-V semiconductor material.

The fin layer 160 and fin layer regrowth 220 can form the two componentsof a vertical fin 190, where the fin layer regrowth 220 formed on thefin layer 160 exposed by removing the dummy gate layer 180 can be inphysical and electrical contact with the fin layer regrowth 220 underthe source/drains 200.

FIG. 18 is a cross-sectional side view showing the fin layer regrowth onthe fin layers along the A-A cutting plane of FIG. 17, in accordancewith an embodiment of the present invention.

In one or more embodiments, the fin regrowth layer 220 can have athickness in the range of about 6 nm to about 25 nm, or in the range ofabout 10 nm to about 20 nm, where the thickness of the fin regrowthlayer 220 is sufficient to cover the rough surface 167 and reduce theroughness of the exposed surfaces of the vertical fins 190.

In various embodiments, the oxide layer 129 can be formed on the finmandrel slabs 125, where the oxide layer 129 can be a native oxide thatformed on the fin mandrel slabs 125 during processing. The oxide layer129 can be thinner than the depth of the gap between the bottom surfaceof the source/drains 200 or merged source/drain 200 and the top surfaceof the fin mandrel slab 125, so there can still be a gap between the finregrowth layer 220 and surface of the oxide layer 129, or the oxidelayer can be sufficiently thick to fill the gap. The oxide layer 129 canprevent formation of the III-V fin layer regrowth 220 on the fin mandrelslabs 125.

In one or more embodiments, the width of the vertical fin 190 can bereduced using a digital etch, where the III-V semiconductor structurecan be thinned using a two-step plasma oxidation and acid etch.

FIG. 19 is a top view showing a gate structure formed on the middlesection of the vertical fins, in accordance with an embodiment of thepresent invention.

In one or more embodiments, a gate structure can be formed on thevertical fins formed by the fin layer 160 and fin regrowth layer 220forming the vertical fins 190. The gate structure can be formed bydepositing a gate dielectric layer on the exposed portions of thevertical fins 190, depositing a work metal layer on the gate dielectriclayer, and depositing a conductive gate fill on the work function layer.A CMP can be used to remove excess conductive gate fill and planarizethe conductive gate fill at the level of the top of the cover layers210.

In various embodiments, electrical contacts can be formed to thesource/drains 200 and the gate structure.

The present embodiments can include a design for an integrated circuitchip, which can be created in a graphical computer programming language,and stored in a computer storage medium (such as a disk, tape, physicalhard drive, or virtual hard drive such as in a storage access network).If the designer does not fabricate chips or the photolithographic masksused to fabricate chips, the designer can transmit the resulting designby physical means (e.g., by providing a copy of the storage mediumstoring the design) or electronically (e.g., through the Internet) tosuch entities, directly or indirectly. The stored design is thenconverted into the appropriate format (e.g., GDSII) for the fabricationof photolithographic masks, which typically include multiple copies ofthe chip design in question that are to be formed on a wafer. Thephotolithographic masks are utilized to define areas of the wafer(and/or the layers thereon) to be etched or otherwise processed.

Methods as described herein can be used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case, the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case, the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

It should also be understood that material compounds will be describedin terms of listed elements, e.g., SiGe. These compounds includedifferent proportions of the elements within the compound, e.g., SiGeincludes Si_(x)Ge_(1-x) where x is less than or equal to 1, etc. Inaddition, other elements can be included in the compound and stillfunction in accordance with the present principles. The compounds withadditional elements will be referred to herein as alloys.

Reference in the specification to “one embodiment” or “an embodiment”,as well as other variations thereof, means that a particular feature,structure, characteristic, and so forth described in connection with theembodiment is included in at least one embodiment. Thus, the appearancesof the phrase “in one embodiment” or “in an embodiment”, as well anyother variations, appearing in various places throughout thespecification are not necessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This can be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes” and/or “including,” when usedherein, specify the presence of stated features, integers, steps,operations, elements and/or components, but do not preclude the presenceor addition of one or more other features, integers, steps, operations,elements, components and/or groups thereof.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper,” and the like, can be used herein for ease of description todescribe one element's or feature's relationship to another element(s)or feature(s) as illustrated in the FIGS. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the FIGS. For example, if the device in theFIGS. is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the term “below” can encompass both an orientation ofabove and below. The device can be otherwise oriented (rotated 90degrees or at other orientations), and the spatially relativedescriptors used herein can be interpreted accordingly. In addition, itwill also be understood that when a layer is referred to as being“between” two layers, it can be the only layer between the two layers,or one or more intervening layers can also be present.

It will be understood that, although the terms first, second, etc. canbe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another element. Thus, a first element discussed belowcould be termed a second element without departing from the scope of thepresent concept.

It will also be understood that when an element such as a layer, regionor substrate is referred to as being “on” or “over” another element, itcan be directly on the other element or intervening elements can also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “connected” or “coupled” to another element, it canbe directly connected or coupled to the other element or interveningelements can be present. In contrast, when an element is referred to asbeing “directly connected” or “directly coupled” to another element,there are no intervening elements present.

Having described preferred embodiments of a device and method offabricating a device (which are intended to be illustrative and notlimiting), it is noted that modifications and variations can be made bypersons skilled in the art in light of the above teachings. It istherefore to be understood that changes may be made in the particularembodiments disclosed which are within the scope of the invention asoutlined by the appended claims. Having thus described aspects of theinvention, with the details and particularity required by the patentlaws, what is claimed and desired protected by Letters Patent is setforth in the appended claims.

1. A method of forming a III-V semiconductor vertical fin, comprising:forming a fin mandrel on a substrate; forming a spacer layer on thesubstrate surrounding the fin mandrel; forming a wetting layer on eachof the sidewalls of the fin mandrel; aiming a fin layer on each of thewetting layers; removing the fin mandrel; removing the wetting layer oneach of the fin layers; and forming a fin layer regrowth on each of thesidewalls of the fin layers exposed by removing the wetting layer fromeach of the fin layers.
 2. The method of claim 1, wherein the wettinglayers are made of aluminum arsenide (AlAs) or indium phosphide (InP).3. The method of claim 2, wherein the wetting layers are formed bymetal-organic chemical vapor deposition (MOCVD) or atomic layerdeposition/atomic layer epitaxy (ALD/ALE).
 4. The method of claim 1,wherein the fin layers are a III-V semiconductor material.
 5. The methodof claim 4, wherein the material of the fin layers are selected from thegroup consisting of indium phosphide (InP), indium arsenide (InAs),indium-gallium-arsenide (InGaAs), and combinations thereof.
 6. Themethod of claim 5, wherein the fin layers are formed by metal-organicchemical vapor deposition (MOCVD) or atomic layer deposition/atomiclayer epitaxy (ALD/ALE).
 7. The method of claim 6, wherein the finmandrel is made of single crystal silicon, and the wetting layer isformed on a {111} crystal face of the fin mandrel.
 8. The method ofclaim 6, wherein the fin layer regrowths are made of the same materialas the fin layers.
 9. The method of claim 6, wherein the fin layerregrowths have a thickness in the range of about 6 nm to about 25 nm.10. A method of forming a III-V semiconductor vertical fin, comprising:forming a fin mandrel on a substrate; forming a spacer layer on thesubstrate surrounding the fin mandrel; forming a wetting layer on eachof the sidewalls of the fin mandrel; forming a fin layer on each of thewetting layers, where the fin layer is a binary or ternary III-Vsemiconductor material; removing the fin mandrel; removing the wettinglayer on each of the fin layers; forming a fin layer regrowth on each ofthe sidewalls of the fin layers exposed by removing the wetting layerfrom each of the fin layers; and forming a dummy gate layer over amiddle section of a vertical fin including the fin layer regrowth andthe fin layer.
 11. The method of claim 10, wherein the material of thefin layers are selected from the group consisting of indium phosphide(InP), indium arsenide (InAs), indium-gallium-arsenide (InGaAs), andcombinations thereof.
 12. The method of claim 11, wherein the finmandrel is made of single crystal silicon, and the wetting layer isformed on a {111} crystal face of the fin mandrel.
 13. The method ofclaim 12, further comprising forming a source/drain on the oppositesides of the dummy gate layer on the exposed portions of the fin layerand fin layer regrowth forming the vertical fin.
 14. The method of claim13, wherein the source/drain on each of the opposite sides of the dummygate layer are made of the same III-V semiconductor material as the finlayers.
 15. The method of claim 14, further comprising removing thedummy gate layer, and forming a gate structure over the middle sectionof the vertical fin. 16-20. (canceled)